Doorstops are, in general, relatively commonplace devices that have been in use for many years. The term doorstop is used to refer to both devices for propping doors open and devices for limiting the travel of doors. The present invention concerns a doorstop in the second sense of the word.
Over the years, a number of devices have been employed to limit the travel of a hinged door. They are familiar household and office items. Conventional construction practices normally provide hinged doors in locations where they can be rotated on their hinges far enough to collide with a wall, another door, or a nearby piece of furniture. Common experience teaches that, depending on the distance from the door hinges to the nearest intersecting wall, the edge of the door or its knob hardware can hit or penetrate the material of an adjacent wall. Also, even if the knob hardware is not arranged so as to impact a wall, the leading edge of a door being swung open can, unless otherwise restrained, hit the baseboard on an adjacent wall, chipping paint off of same, and gouging and otherwise damaging the baseboard. Furthermore, in situations in which cabinetry, furniture, or other objects need to be placed in the potential path of travel of the door as it rotates on its hinges, it is desirable to provide an apparatus that limits the travel of the door so as to prevent damaging collisions.
There are a number of doorstop devices known in the prior art. While not always safe, they are generally effective. However, most such devices have one or more drawbacks. One of the most common devices used for many years is a straight post secured to a wall or baseboard, the distal end of which is terminated with a non-abrasive resilient compressible or deformable pad. Such devices were generally formed of a metal or wood shank with a threaded wood screw section at one end that is screwed into the baseboard or wall. The distal end of the apparatus is terminated with a pad that strikes the door as it swung open, preventing same from hitting the wall or the baseboard. While these have been successfully used for many years, they have two significant drawbacks. The first is the fact that all the deformability of the structure resides in the pad. Therefore, it tends to be rather stiff. If a door is swung open at a high rate of speed, as it often is when children open a door with excessive enthusiasm, the relatively small contact area and relative stiffness of these devices tend to make an unattractive indentation in a door at the point at which it contacts the pad. Furthermore, as hollow doors have become more and more common in modern residential construction, there has been a greater problem with the potential of such devices puncturing a door when it hits a stop with excessive speed.
A second major drawback of such doorstops is the fact that they are, by their nature, a solid piece of metal firmly secured to a baseboard at about ankle height. Many people are familiar with the painful injuries that are encountered by accidentally running into a doorstop of this type.
The second of the above noted drawbacks is addressed by a modern version of this type of doorstop in which the shaft is formed of a relatively stiff coiled spring. The spring is arranged so that its coils are in complete contact when it is unflexed and it forms a straight shaft under these conditions. Therefore, the geometry of the shaft is stable under forces that are applied to the end of the shaft parallel to its longitudinal axis. This is the direction of force applied by the plane of a door striking the end pad of such a doorstop where the plane of the door is approximately perpendicular to the longitudinal axis of the stop. However, the spring structure will bend and give way in response to forces that are off axis to a considerable degree. Thus, the accidental striking of such a stop as one walks parallel to the wall to which it is affixed normally creates only surprise, rather than painful injuries to the foot, as the spring gives way and bends when one's foot or ankle strikes it. However, it still has the problem of a relatively small contact area and limited resilient deformable material on the end pad that will tend to mar a door that contacts it with sufficient force a sufficient number of times.
More recently, stops have been employed for mounting directly on the hinge pin of a door and providing two shock absorbing pads that intersect a plane of rotation of the structure about the hinge pin. Typically, one pad is fixed relative to the eye through which the hinge pin of the door passes and the other is mounted on a threaded shaft so that the angular distance between the flat face of its pad and the flat face of the fixed pad may be adjusted. By employing this structure, the angle to which the door may be opened before one pad encounters the door and the other pad encounters an adjacent face of a door jamb may be adjusted so as to selectively limit the travel of the door while still assuring that the door surface engages the pad at the desired angle. These are particularly designed to be used in relatively close quarters where a door might, for example, strike a cabinet or other fixture in a bathroom if it is opened too far.
These devices have the advantage of avoiding horizontal protrusions from baseboards or walls that are a necessary part of the use of the other types of stops described hereinabove. The principal drawback of this third type of stop is the fact that the padded surface engaging both the door and the adjacent door jamb or wall is very close to the pivot point of the door hinge. As a result, the width of the door extending from the hinge to the handle acts as a long lever arm that gives the door a large mechanical advantage. In other words, the door acts as a long lever that tends to put very large forces on the small surface areas of the pads that contact the door and the door jamb. This increases the propensity of such devices to gouge both the door and the adjacent jamb, particularly under the influence of enthusiastic openings by children. Experience has also taught that these devices lack the positive stop action one gets from a more conventional post type doorstop. As a result, children can often be seen bouncing on a door that is equipped with this type of stop as it feels spring loaded to them. Furthermore, because of the large mechanical advantage created by the lever arm of the door against the stop, these stops tend to break more frequently than other doorstops.
Half round stops protruding from a floor are also known. These have an advantage of a somewhat higher surface area for encountering the door. However, they create a potential hazard in the floor and are deemed unsightly by many people. They are most commonly used in office environments as opposed to residences.
In particular, the inventor of the present invention encountered a recurring problem with half round doorstops set in concrete floors in commercial office buildings that motivated his consideration of the inadequacy of prior art doorstops. In most commercial construction, the basic flooring in office and warehouse space is a concrete slab. Doorstops are installed in such slab flooring by using a masonry bit to drill holes into which lead inserts are placed that function to expand like molly bolts. Screws are then passed through holes in the base of the half round stops into the lead inserts. The threads of the screws can cut the lead, and the insertion of the screw shaft into the lead causes it to expand and become securely wedged in the hole in the concrete. If the appropriate size combination is not made for lead insert and screw, the fitting can either be too loose, or can fracture the concrete.
It is the inventor's experience that severe impacts of doors against such half round stops have a tendency to cause the frangible concrete to shatter around the lead insert and the doorstop to thus be loosened. The conventional method of repair is to remove the old lead insert, drill a somewhat larger hole in the concrete and insert a larger lead insert for the next installation. This is labor intensive and quite inconvenient. Experience further indicated that the same sort of activity that caused the door to strike the doorstop with sufficient force to crack the concrete around the lead insert was often applied at a time when the doorstop was loose or removed awaiting repair, causing the door to be thrown into the wall that the stop formerly protected, with unfortunate and destructive results. Therefore, while the present invention is certainly not limited to applicability in commercial settings, the original motivation for creating same arose as a result of problems the inventor encountered with conventional floor installed doorstops.
U.S. Pat. No. 442,759 to H. W. Struss showed a two part doorstop that included a curved spring surface with a free end passing through an eye bolt. It was usable both as a door-to-door protective stop or a door-to-wall stop. The eye bolt was used to prevent the free end of the curved spring from encountering the door, and to give support so as to minimize stress on the spring when under compression.
While doorstops are relatively commonplace, the need for same remains. Replacement of baseboard and sheet rock, plaster repair, and the like are expensive jobs. It is highly desirable to have an improved doorstop that is simple and inexpensive to manufacture yet both safe and effective for use in a residence. Furthermore, it is desirable to have such a device that will cause less damage at its point of contact with the door that it encounters than has been conventionally caused by prior art stops, yet can absorb and dissipate the relatively high energy of a door being swung open too rapidly, as is often the case when children open doors.